Solar Cycle Variability in
MLS Carbon Monoxide (CO)
Jae N. Lee1 , Dong L. Wu2, and Alexander Ruzmaikin3
1. Joint Center for Earth Systems Technology, University of
Maryland, Baltimore County, Baltimore, MD
2. NASA Goddard Space Flight Center, Greenbelt, MD
3. Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA
9/19/12
SORCE Science Meeting, Annapolis
CO chemistry and transport in the middle atmosphere
After Allen et al. [1999]
source
CO2 + hn ® CO +O
CO +O + M ® CO2 + M
Thermosphere
Mesosphere
diffusion
Stratosphere
Summer
9/19/12
CH 4 ¾oxidation
¾¾¾
®CO
Annapolis
CO +OHSORCE
®Science
COMeeting,
2 +H
Winter
Polar Night
Motivation
 New observations from Aura MLS (Microwave
Limb Sounder) and SORCE TIM providing
accurate measurements of atmospheric
tracers and total solar irradiance
 To what extent has the solar cycle contribute
to MLS CO variability during 2004 - 2011? If
CO changes with TSI, how does this effect vary
with season and location?
9/19/12
SORCE Science Meeting, Annapolis
MLS CO distribution
December mean MLS CO
July mean MLS CO
 Chemical balance between the source and the sink leads to the strong
vertical gradient of CO mixing ratio with abundant CO in the mesosphere
 Decent in the polar region brings high CO from the mesosphere
 Long CO life time helps to maintain vertical and horizontal gradients
9/19/12
SORCE Science Meeting, Annapolis
Interannual variations of MLS CO and SORCE TSI
Winter
time mean MLS CO at 0.005hPa
SORCE TSI and MLS CO at 0.005hPa
1362.5
28
26
1361.5
24
1361
22
2
TSI (W/m )
1362
1360.5
2004
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2005
2006
2007
2008
2009
2010
2011
2012
CO volume mixing ratio (ppmv)
82N December
CO*1.2 +6 : 82S July
CO : NH
SH
20
2013
SORCE Science Meeting, Annapolis
 Strong interannual
variability
 ~16% increase
from 22 ppmv to
26 ppmv since
2009
 TSI variation on
photolysis and
transport from the
low thermosphere
likely play role
CO correlations with SORCE TSI
(2004-2011)
(c) r December
between CO and
TSI : Dec
July (2004-2011)
(d) r between
CO and TSI : Jul
0.5
0.01hPa
0.01hPa
0.45
0.1hPa
0.1hPa
0.4
1hPa
1hPa
0.35
10hPa
300hPa
80S
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10hPa
40S
0
40N
80N
300hPa
80S
0.3
40S
0
40N
80N
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0.25
 Significant correlations
between CO and TSI
(95% level)
 Solar signal extends to
upper stratosphere
 Likely from the indirect
responses to the solar
forcing as a result of
dynamical transport
 No negative
correlation suggesting
that CO increase with
TSI
Regression of MLS CO on SORCE TSI
Regressed Amplitude
 Estimate the sensitivity
of CO to solar
irradiance by
regressing CO amount
(ppmv per W/m2)
 Maximum CO response
to 1 w/m2 of TSI
(~0.07%) can be as
high as 3 ppmv (~10%)
at 80km
 Amplified CO
responses
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December (2004-2011)
(e) Regressed Amplitude : CO : Dec
July (2004-2011)
(f) Regressed Amplitude : CO : Jul
3
0.01hPa
0.01hPa
2.5
0.1hPa
0.1hPa
1hPa
1hPa
2
1.5
1
10hPa
10hPa
0.5
300hPa
80S
40S
0
40N
80N
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300hPa
80S
40S
0
40N
80N
0
Sensitivity of CO to TSI
CO change at 82N (%/%)
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MLS
345 (0.005 hPa)
WACCM/SRPM SSI
325 (82 km)
WACCM/NRL SSI
392 (82 km)
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conclusions
 Observations from Aura MLS (Microwave Limb
Sounder) and SORCE TIM showing statistically
significant positive correlation between CO and TSI
 CO is in phase with TSI. More UV produces more CO
which is transported downward.
9/19/12
SORCE Science Meeting, Annapolis
Acknowledgment
 Living With a Star Program
 MLS and LASP team for data support
 SORCE
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SORCE Science Meeting, Annapolis
Back ups
Lagged correlation between MLS CO and SORCE TSI
Lagged correlation 56N : December 2009
 Vertical polar descent may cause a delayed CO response to the
short term solar forcing
 Estimate this delay by lagged correlation
 Maximum correlation day increases from 3days in the upper
mesosphere to 17 days in the lower mesosphere
 This descent rate (~1.1km/day) compares will with those estimated
from the downward propagation
of maximum CO NAM index
9/19/12
SORCE Science Meeting, Annapolis
Chemistry
 CO in the middle atmosphere comes from CO2 photolysis
 Source in thermosphere
CO2 + hn ® CO +O
 Chemical loss of CO
CO +O + M ® CO2 + M
 Methane oxidation source in the stratosphere, but destroyed
by OH during the sunlit hours
CO +OH ® CO2 + H
9/19/12
SORCE Science Meeting, Annapolis